Conventionally, as a method for adding a dopant to a silicon crystal, a method of lowering a sample chamber housing a sublimable dopant down to a predetermined position above a melt in a pulling furnace, heating and subliming a sublimable dopant by radiant heat from the melt, and introducing the sublimable dopant, which is sublimed to the gaseous form, into the melt has been adopted.
As a method for introducing the dopant in the gaseous form to a melt, a method in which an open end of a supply pipe is disposed above the melt and the dopant carried by a carrier gas composed of an inert gas such as argon gas is sprayed from the supply pipe toward the melt, can be exemplified.
According to the invention disclosed in Patent Document 1, a sample tube (doping tube) is disposed at a position that does not interfere with a pulling mechanism and the sample tube is lowered down to just above an upper face of a crucible, thereby melting a dopant inside the sample tube by radiant heat from the melt at this position. Thereafter, the sample tube storing the dopant is lowered to a position so as to be dipped in the melt, thereby adding the melted dopant to the melt from an open surface of the doping tube. A silicon single crystal ingot having a discontinuous range of specific resistivities in a growing direction is thus pulled and grown.
[Patent Document 1] Japanese Unexamined Patent Application Publication No. 2005-336020